1. Field of Invention
This invention relates generally to a fabric for producing outerwear garments suitable for wear in outdoor environments exposing the wearer to water as well as to cold temperatures, and more particularly to a light-weight thermally-insulated fabric of this type which is water-resistant, buoyant and quick-drying.
2. Status of Prior Art
On boats, beaches, hiking trails and in other outdoor environments in which a wearer of an outerwear garment is exposed to rain or water as well as to cold temperatures, the garment should be capable of coping with all aspects of this environment.
A suitable outerwear garment for cold climates is a field jacket having an outer shell of waterproof fabric, such as a sheet of woven nylon laminated to a plastic film, and an inner liner of thermal insulation material, such as wool padding. A field jacket of this type is relatively heavy, but that is not its only drawback. The waterproof shell of the jacket is not permeable to vapor. Hence should the wearer be engaged in strenuous activity causing him to sweat, the resultant vapor from the body of the wearer will not be released from the jacket and its wearer will become clammy and uncomfortable.
And should the wearer of this jacket be on a boat and fall overboard, the jacket then offers the wearer no protection, for the wool liner will become saturated with water and weigh the wearer down rather than providing buoyancy to keep the wearer afloat.
Also when the wool liner becomes saturated with water and one then squeezes out the water in order to dry out the jacket, the jacket is then very slow to dry out, for residual moisture retained by the wool after the water is squeezed out, is entrapped in the interstices of the tangled wool fibers.
An outerwear garment adapted to keep a wearer warm requires thermal insulation. The reason a wool sweater or a cotton sweatshirt provides warmth is that the natural fibers of these garments having myriad still air pockets dispersed throughout the fabric. Heat flows from a site of higher temperature to one of lower temperature mainly by conduction through a solid and by convection, that is, by the flow of a fluid carrying heat. The conductance of natural fibers is low and the still air pockets therein greatly reduce convection.
But the properties of fabrics made of natural fibers which result in good thermal insulation also give these fabrics slow drying characteristics. When a wet wool garment, such as a swim suit is squeezed to expel water therefrom, the residual moisture entrapped in the interstices of the wool is very slow to evaporate.
With outerwear garments intended for wear on boats and in other environments in which the wearer runs the risk of falling into the sea, one must take into account whether the garment offers the wearer any protection in this situation. Should the wearer who falls into the sea be wearing a heavy overcoat, the overcoat will become saturated with water and lack buoyancy. This also applies to conventional sweatshirts and field jackets worn by the wearer.
Of prior art interest are life preservers made of kapok. Kapok is a silky fiber that surrounds the seeds of a kapok tree. A significant feature of a fabric in accordance with the invention is that its buoyancy approaches that of kapok, yet can be tailored to create an outerwear garment of any desired type.